The recipe makes two large drinks. If you were at Starbucks, we’re talking two venti drinks. Feel free to halve the recipe, or quarter it, if you’re not as much of a java addict or power drinker.
I recommend making the full recipe and putting the extra portion in the freezer, and the next time you want one, it’s ready. No need to dirty the blender. All you have to do is let it unthaw a bit, either 30 minutes at room temp or about 1 minute in the microwave. Or you can kind of pick at it, granita-style.